Emergence of a Big Bang singularity in an exact string background

TL;DR

This paper explores how a Big Bang singularity in 3+1 dimensions can be understood through an exact string theory background, revealing higher-dimensional structures that resolve the singularity.

Contribution

It demonstrates that the Big Bang singularity arises from higher-dimensional orbifold singularities, with an effective 3+1D description breaking down near the compactification scale.

Findings

Higher-dimensional orbifold singularities resolve 3+1D curvature singularities.

A bouncing universe emerges in 5 or more dimensions.

String theory background excises singularities via tachyon potentials.

Abstract

The origin of Big Bang singularity in 3+1 dimensions can be understood in an exact string theory background obtained by an analytic continuation of a cigar like geometry with a nontrivial dilaton. In a T-dual conformal field theory picture there exists a closed string tachyon potential which excises the singular space-time of a strongly coupled regime to ensure that a higher dimensional universe has no curvature singularity. However in 3+1 dimensions the universe exhibits all the pathology of a standard Big Bang cosmology. The emergence of a singularity now owes to a higher dimensional orbifold singularity which does not have a curvature singularity in higher dimensions, suggesting that close to the compactification scale an effective description of 3+1 dimensions breaks down and bouncing universe emerges in 5 and higher dimensions.